Date   

Re: Pair of P6101 Scope Probes

 

Thanks to all who responded.
The probes are spoken for.
Dennis

_____________________________________________
From: Dennis Tillman W7pF [mailto:dennis@ridesoft.com]
Sent: Tuesday, May 18, 2021 9:35 PM
To: TekScopes@groups.io
Subject: Pair of P6101 Scope Probes


I found a pair of P6101 scope probes which I have no use for.
They appear to be functional. The only cosmetic problem they have is the
cables need to be cleaned. The plastic seems to have a thin coating of
whitewash on it. This is probably due to age. I have seen this before and a
good wipe with a mild solvent gets rid of it.

These are 1X, 1 meter general purpose probes. They are capable of at least
34MHz. They have no intrinsic resistance of their own apart from the
distributed 180 ohms of the inner conductor so the input impedance of the
probe is whatever the input impedance of the scope's amplifier is. The cable
has 32pF of capacitance.
I have 10" ground leads for them but no other accessories.

A manual is at https://w140.com/tekwiki/images/f/f4/P6101.pdf.

You can have the pair for $20 plus shipping in a Priority Mail Small Flat
Rate Box which costs about $8 to mail anywhere in the USA. I don't know what
the postage will be to Canada in the same box.

Contact me off-list at dennis at ridesoft dot com if you want them.

Dennis


Re: Tek 577 Step Gen & Volt Div knobs skirt pictures needed

Rogerio O
 

Hi Folks,
I have been trying to fix the problem on my 577/177 so I had no time to check the forum.
It has been more difficult to spot the problem than I thought at first.
During this process I had the opportunity of watching one of the tantalum caps catch on fire.
Fortunately it did to take any other component down with it.
I have already bought the celluloid film so I can try to print the images.
No need to worry about scaling since photoshop allows me to define the image size.
I intend to continue trying to fix the electronics first, then move to "cosmetics", so it may take some time before I start it but I will post photos as soon as I make the replacements.
Thank you all for your help.


Re: New Chat: Question: Understanding a scope probe #chat-notice

Jean-Paul
 

Can we please use the normal message board, and NOT chats? A bit confusing.

To OP Henry:

VTVMs had various Zin and probes, some had different Rprobe in AC and DC inputs.

Best ref for scope probes in general:

Tektronix Circuit Concepts "Oscilloscope Probe Circuits Concepts" everything from passive/active/Zo, DC-many GHz.

https://w140.com/tekwiki/images/6/62/062-1146-00.pdf

Worthwhile to have the printed booklet.

Jon


"Chats"

 

Dennis can I suggest these be disabled as they aren't part of the main email
stream.

David


Re: New Chat: Question: Understanding a scope probe #chat-notice

Tom Lee
 

In a word, bandwidth. VTVM's don't need it, scopes do.

If you want the nitty-gritty, email me off list and I'll send you a writeup with more detail than anyone wants.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 5/18/2021 23:03, TekScopes@groups.io Notification wrote:

A new chat has been created:

New

I would like to better understand the components in a scope probe. But first I should clarify my beliefs about a VTVM. As I understand it, most VTVM's have a plain ordinary wire with a pointed probe tip. Any wire would do. The probe runs into the VTVM, where the first thing the signal goes through is an 11Mohm resistor, before going on to an amplifier to run the meter that reads out the voltage. The purpose of the amplifier being to amplify the signal by an amount that compensates for the gigantic drop in strength from the 11Mohm resistor, so that the meter reads actual voltage. The purpose being to sample a very tiny amount of "water running through a pipe" to give a pressure reading. Compared to a regular VOM which would require such a large amount of "water in a pipe", that it would actually cause a drop in "water pressure" just to run the meter, that the reading would be useless. Have I made a good analogy? If so, why does an oscilloscope probe utilize a capacitor in parallel with the 11Mohm resistor, when the VTVM doesn't? What is the purpose of that capacitor? Thank you.

*By:* henryfinley <tomsradio@gmx.com>

View/Join This Chat <https://groups.io/g/TekScopes/chat/8133>

Do not reply to this message to post to the chat. You can participate in chats only through the group's website.


New Chat: Question: Understanding a scope probe #chat-notice

TekScopes@groups.io Notification <noreply@...>
 

A new chat has been created:

New

I would like to better understand the components in a scope probe. But first I should clarify my beliefs about a VTVM. As I understand it, most VTVM's have a plain ordinary wire with a pointed probe tip. Any wire would do. The probe runs into the VTVM, where the first thing the signal goes through is an 11Mohm resistor, before going on to an amplifier to run the meter that reads out the voltage. The purpose of the amplifier being to amplify the signal by an amount that compensates for the gigantic drop in strength from the 11Mohm resistor, so that the meter reads actual voltage. The purpose being to sample a very tiny amount of "water running through a pipe" to give a pressure reading. Compared to a regular VOM which would require such a large amount of "water in a pipe", that it would actually cause a drop in "water pressure" just to run the meter, that the reading would be useless. Have I made a good analogy? If so, why does an oscilloscope probe utilize a capacitor in parallel with the 11Mohm resistor, when the VTVM doesn't? What is the purpose of that capacitor? Thank you.

By: henryfinley <tomsradio@...>

View/Join This Chat

Do not reply to this message to post to the chat. You can participate in chats only through the group's website.


Pair of P6101 Scope Probes

 

I found a pair of P6101 scope probes which I have no use for.
They appear to be functional. The only cosmetic problem they have is the
cables need to be cleaned. The plastic seems to have a thin coating of
whitewash on it. This is probably due to age. I have seen this before and a
good wipe with a mild solvent gets rid of it.

These are 1X, 1 meter general purpose probes. They are capable of at least
34MHz. They have no intrinsic resistance of their own apart from the
distributed 180 ohms of the inner conductor so the input impedance of the
probe is whatever the input impedance of the scope's amplifier is. The cable
has 32pF of capacitance.
I have 10" ground leads for them but no other accessories.

A manual is at https://w140.com/tekwiki/images/f/f4/P6101.pdf.

You can have the pair for $20 plus shipping in a Priority Mail Small Flat
Rate Box which costs about $8 to mail anywhere in the USA. I don't know what
the postage will be to Canada in the same box.

Contact me off-list at dennis at ridesoft dot com if you want them.

Dennis


Re: Looking for sensitive audio RMS meter

 

Great to hear about that - thanks for sharing. I'm sure I'll have a
lot of questions about audio for you in the future :-)

On Tue, May 18, 2021 at 9:52 PM Ted Rook <rooknrol@warwick.net> wrote:

Hello again cheater, one of your messages found its way into my spam folder for some
reason, I found it today. Some replies are interspersed again.....


On 15 May 2021 at 5:18, cheater cheater wrote:

On Sat, May 15, 2021 at 1:16 AM Ted Rook <rooknrol@warwick.net> wrote:

On 14 May 2021 at 2:26, cheater cheater wrote:

Thanks again Ted. I didn't know you worked at A&H.
When I was there we were a very small operation, in the 1970s maybe a dozen people total. I
was a live sound technician (roadie) which in those far off simple days qualified me for the
test department (which was a new development, business was good) where I learned to drive
a scope a voltmeter and a signal generator. Later I contributed to development of new
designs for live and recording mixers evaluating prototypes designed out of house, then later
still developing new prototypes from the ground up inhouse. I worked in London at two
locations and in Brighton, by which time we had a factory in Cornwall that is still the company
HQ.
What a great story. What do you think were the most interesting
circuits you designed there?
the most interesting for me (as distinct from a customer's viewpoint) was the discrete
transistor system for the AH Syncon recording mixer. This was in the late 1970s before high
quality opamps were available at prices competitive with discrete, we wanted amplifiers that
delivered near-theoretical low noise from the mic amps, would operate on +/- 24V DC internal
DC supplies to provide increased maximum level before clipping (+26dBv internally and
+24dBm at outputs), in 1978 this required discrete transistors. The closest opamps were the
new Philips device that became the NE5534, however the prices of these were higher than
our budget. From the designers of those circuits I learned a lot, the Syncon project was a
huge step up in technical quality for A+H. With the knowledge and skill learned with Syncon
we were able to take on another technically demanding project developing analogue
hardware for FM radio systems, the MBI product range, later absorbed by Soundcraft.


I've had a few more questions about the meter as well, if that's OK.

You say the TM3B is single-ended, not balanced. What does that
actually mean for a device that's battery powered and essentially
floating? I could connect the Bryston 10B's XLR output - the hot and
cold pins - to the input of the TM3B. Isn't that balanced?
Yes, the meter itself is floating however once connections are made to scope/listening device
at the meter output terminals grounding via the meter probe common enters the picture.


My PMC / Bryston 10B only has symmetrical balanced XLR outputs. If I
wanted to measure the noise, what should I measure: between hot and
cold, gnd and hot, gnd and cold?
Hot and cold. The voltage between ground and one of the phases alone is half amplitude,
-6dB.


You mention using a small listening device for listening from the
TM3B's output. That's a really good idea. I shall use a small desktop
monitor. But maybe I should use a battery powered speaker, that should
prevent any ground loops. What do you think?
Yes that would work for the listening device but leaves the scope ground as a source of
grounding.
I was wondering why you mention scope ground. Are you saying I should
use the TM3B and hook up a scope and a listening device to its output,
both to the same port?
Our typical hookup was exactly that, scope BNC input driven from the TM3B output and the
same terminal used similtaneously for the connection to an amp and loudspeaker.

Ted


First find out how it behaves 'out of the box'. A good brand like Bryston probably takes care to
eliminate contamination with ripple and hum at the design phase.
That's the plan, thanks!










Re: Looking for sensitive audio RMS meter

Ted Rook
 

Hello again cheater, one of your messages found its way into my spam folder for some
reason, I found it today. Some replies are interspersed again.....


On 15 May 2021 at 5:18, cheater cheater wrote:

On Sat, May 15, 2021 at 1:16 AM Ted Rook <rooknrol@warwick.net> wrote:

On 14 May 2021 at 2:26, cheater cheater wrote:

Thanks again Ted. I didn't know you worked at A&H.
When I was there we were a very small operation, in the 1970s maybe a dozen people total. I
was a live sound technician (roadie) which in those far off simple days qualified me for the
test department (which was a new development, business was good) where I learned to drive
a scope a voltmeter and a signal generator. Later I contributed to development of new
designs for live and recording mixers evaluating prototypes designed out of house, then later
still developing new prototypes from the ground up inhouse. I worked in London at two
locations and in Brighton, by which time we had a factory in Cornwall that is still the company
HQ.
What a great story. What do you think were the most interesting
circuits you designed there?
the most interesting for me (as distinct from a customer's viewpoint) was the discrete
transistor system for the AH Syncon recording mixer. This was in the late 1970s before high
quality opamps were available at prices competitive with discrete, we wanted amplifiers that
delivered near-theoretical low noise from the mic amps, would operate on +/- 24V DC internal
DC supplies to provide increased maximum level before clipping (+26dBv internally and
+24dBm at outputs), in 1978 this required discrete transistors. The closest opamps were the
new Philips device that became the NE5534, however the prices of these were higher than
our budget. From the designers of those circuits I learned a lot, the Syncon project was a
huge step up in technical quality for A+H. With the knowledge and skill learned with Syncon
we were able to take on another technically demanding project developing analogue
hardware for FM radio systems, the MBI product range, later absorbed by Soundcraft.


I've had a few more questions about the meter as well, if that's OK.

You say the TM3B is single-ended, not balanced. What does that
actually mean for a device that's battery powered and essentially
floating? I could connect the Bryston 10B's XLR output - the hot and
cold pins - to the input of the TM3B. Isn't that balanced?
Yes, the meter itself is floating however once connections are made to scope/listening device
at the meter output terminals grounding via the meter probe common enters the picture.


My PMC / Bryston 10B only has symmetrical balanced XLR outputs. If I
wanted to measure the noise, what should I measure: between hot and
cold, gnd and hot, gnd and cold?
Hot and cold. The voltage between ground and one of the phases alone is half amplitude,
-6dB.


You mention using a small listening device for listening from the
TM3B's output. That's a really good idea. I shall use a small desktop
monitor. But maybe I should use a battery powered speaker, that should
prevent any ground loops. What do you think?
Yes that would work for the listening device but leaves the scope ground as a source of
grounding.
I was wondering why you mention scope ground. Are you saying I should
use the TM3B and hook up a scope and a listening device to its output,
both to the same port?
Our typical hookup was exactly that, scope BNC input driven from the TM3B output and the
same terminal used similtaneously for the connection to an amp and loudspeaker.

Ted


First find out how it behaves 'out of the box'. A good brand like Bryston probably takes care to
eliminate contamination with ripple and hum at the design phase.
That's the plan, thanks!





Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

@Antonio90
 

I was just going to ask about that. Yeah, it is strange. And I don't think anyone swapped it, as all the smd ICs are from the 88s.


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

Egge Siert
 

Hi again,

Just looking at the pictures in your Photo-Album. The Main Board has 671-0722-05 as PN and the A5 Controller Board is the new SMD-Version (1988 parts on it). Intriging mix. I have serviced several early 2465B's out of the same era and they all had the old style Controller Board with the separate A4 Read-Out Board.

Greetings,

Egge Siert


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

Egge Siert
 

Hi Antonio,

With many 1988 parts it is an early 2465B with 671-0722-00/05/07 as Main Board (A1) Partnumber. With this Partnumber you can look in the Service Manual (070-6863-01, SN B049999 & below) which Beaverton SN's are relevant for your Guernsey Model.

Greetings,

Egge Siert


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

@Antonio90
 

150140 it is then.
Thank you!


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

Ozan
 

On Tue, May 18, 2021 at 07:06 AM, @Antonio90 wrote:

It is a Guernsey-made model
indeed, but I cannot find the scope's serial number anywhere.
Serial number location is between Ch2 and Ch3 BNC inputs. In your youtube video it is too grainy to tell but I think there is a serial number in that location on your scope too.
Ozan


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

@Antonio90
 

@Ozan
It's a 1988 scope then, or a little bit youger if the IC's are older than the scope.


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

Ozan
 

On Tue, May 18, 2021 at 07:36 AM, @Antonio90 wrote:


Sorry for posting again, don't know how to edit messages.

In the new photos added, there are a lot of 88's. So I'm guessing that's the
year of manufacture of most of them. Maybe a 1990's or so scope?
Usually two digit year, two digit week is marked. For example 8824 -> 24th week of 1988.
Ozan


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

@Antonio90
 

Sorry for posting again, don't know how to edit messages.

In the new photos added, there are a lot of 88's. So I'm guessing that's the year of manufacture of most of them. Maybe a 1990's or so scope?


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

@Antonio90
 

Thank you very much for your answers.

I *might* have found the problem. There is corrossion, gunk, and half-desintegrated components all around U650 (AMI 8843MBV 155-0244-01). I'm leaning towards external damage, IE water, some cleaning solution used around it, or something like that, because there are no electrolytics anywhere close, and the big filter ones would have leaked through the internal frame, which is pristine. Also, there is no corrosion or evaporation residue in the internal part of the PCB.

I will be making a list of the components that need replacing and looking out for equivalent replacements. In the meantime, any tips for cleaning? I read somewhere that a toothbrush and then isopropyl cleans it very well. Let's hope there's no pads or traces destroyed.

Also, what's the proper way of unsocketting ICs without destroying them? I'm guessing the AMI 8843MBV, could benefit from a little cleaning of the pins.

I'm posting some photos of the corrossion in the album, there are quite a few components damaged.

https://groups.io/g/TekScopes/album?id=264175

@Jean-Paul

It cost me 100€, which was a steal compared with the usual european prices for a working 2465B, not so much for a non properly working one I guess.
I want a bench scope for the lab, as it is not really kitted out yet, and this seemed like a good option. I have another non-working 466, will give a go repairing it when I finish with this one. It's a fascinating device really, never seen anything like it.

It self-tests OK at startup, and the rest of self-tests seem to be OK too, but I cannot see it in detail, as the readout screen is shifted up, I can only see the bottom line. Tried adjusting the pots for the position and gain, but the problem has to be elsewhere as I can only move it a little, also there aren't any SMD electrolytics, at least I haven't seen any, they are all through hole.

Will test the dallas ASAP, when I figure out what pins to measure for battery voltage.

@Egge Siert:

Are the production dates printed on the ICs? I will look up the IC markings anyway, to see If I can find production dates. It is a Guernsey-made model indeed, but I cannot find the scope's serial number anywhere.


Re: Tektronix 2465B Square wave noise on active readout. #photo-notice

Egge Siert
 

Hi Antonio,

Serialnumbers are the key to which Service Manuals are relevant. With Guernsey and Heerenveen Models I can sometimes help. Look for Production Dates on IC's and so on.

Greetings,

Egge Siert


Re: GPIB board for calibrating AM503B, or alternatives?

Jared Cabot
 

I've had a look through the document and it makes sense so far, but I just have to figure out all this firmware business and sending the right commands in the right format... I tend to program with solder rather than a keyboard, so it's definitely a learning curve for me. :)

My script will be rather large once it's done (It's sprouting a command line UI) but it can certainly be distributed with the document.
I might look at making a github repository for it soon once I'm not completely embarrassed by the code. hahaha.


Regards,
Jared

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